Per GeekBench numbers the iPads really divide into three groups:
The iPad 1, with a score of 454.
The iPad 2, iPad 3 and iPad Mini with scores of 781, 791 and 745 respectively.
The iPad 4 with a score of 1756.
So if you bought an iPad 2 then you've got a device a shade faster than one of the current generation models. Naturally app makers are therefore still going to optimise for that level of performance.
Conversely if you went out and bought a Motorola Xoom or one of the other early Android tablets then not only did your specific device fail to capture enough of the market to be interesting in itself but also the devices that have powered the subsequent explosion in Android share are noticeably faster (yes, even the Kindle Fire). So app makers are unlikely to spend much time optimising for that level of performance.